Fuel injection systems deliver fuel to the combustion chamber of an engine, where the fuel is thoroughly mixed with air before combustion. One form of fuel injection system well-known in the art is a fuel spray nozzle. Fuel spray nozzles atomise the fuel to ensure its rapid evaporation and burning when mixed with air. However, ensuring efficient combustion of the fuel can be difficult because the velocity of the air stream within the combustion chamber creates a hostile environment for the flame, while the short length of the combustion system means there is little time for burning to occur.
An airblast atomiser nozzle is a type of fuel spray nozzle in which fuel delivered to the combustion chamber by a fuel injector is aerated by swirlers to ensure rapid mixing of fuel and air, and to create a finely atomised fuel spray. The swirlers are designed to create a high level of shear in the fuel flow.
Typically, an airblast atomiser nozzle will have a number of swirler circuits. An annular fuel passage between a pair of swirler circuits feeds fuel onto a pre-filming lip. Thus a sheet of fuel is formed that breaks down into ligaments. These ligaments are then broken up into droplets within the shear layers of the surrounding highly swirling air, to form the fuel spray stream that is emitted from the fuel injection system.
Efficient mixing of air and fuel not only results in higher combustion rates, but also reduces the deposition of unburnt hydrocarbons within the combustion chamber and the formation of exhaust smoke resulting from incomplete combustion of the fuel.
There is a continuing need to enhance the efficiency of gas turbine engines of the type used to power jet aircraft or generate electricity, and thus it is desirable to improve the design of fuel injection systems, such as airblast atomiser nozzles, to achieve higher combustion rates.